1. Field of the Invention
The present invention relates to a method of manufacturing a photosensitive epoxy structure, and more particularly, to a method of manufacturing a photosensitive epoxy structure with a step difference and a through hole by using a photography process and a method of manufacturing an inkjet printhead by using the method of manufacturing a photosensitive epoxy structure.
2. Description of the Related Art
Generally, an inkjet printhead is an apparatus that ejects fine droplets of a printing ink on a desired area of a recording paper in order to print predetermined color images. The inkjet printhead can be classified into two types according to the ejection mechanism of ink droplets. One type is a thermal inkjet printhead that ejects ink droplets by an expansion force of bubbles that are generated from ink by a thermal source, and the other type is a piezoelectric inkjet printhead that ejects ink droplets by applying a pressure generated by deformation of a piezoelectric element to the ink.
The ejection mechanism of ink droplets from a thermal inkjet printhead will now be described in more detail. When a pulse current is applied to a heater formed of a resistive heating material, the heater generates heat, and thus, ink adjacent to the heater is immediately heated to about 300□, thereby generating bubbles due to the boiling of the ink. The bubbles expand and pressurize ink filled in an ink chamber. As a result, ink positioned near a nozzle is ejected in the form of droplets from the ink chamber through the nozzle.
FIG. 1 is a partial plan view illustrating a conventional thermal inkjet printhead, and FIG. 2 is a sectional view taken along line II-II′ of FIG. 1. Referring to FIGS. 1 and 2, the conventional thermal inkjet printhead includes a substrate 10 on which a plurality of material layers are disposed, a chamber layer 20 disposed on the substrate 10, and a nozzle layer 30 disposed on the chamber layer 20. A plurality of ink chambers 22 are formed in the chamber layer 20, and a plurality of nozzles 32 through which ink is ejected are formed in the nozzle layer 30. An ink feed hole 11, for supplying ink to the ink chambers 22, is formed through the substrate 10. A plurality of restrictors 24 are formed in the chamber layer 20 to connect the ink chambers 22 with the ink feed hole 11.
Meanwhile, an insulating layer 12, for insulating the substrate 10 from a plurality of heaters 14, is formed on the substrate 10. The heaters 14 are formed on the insulating layer 12, and electrodes 16, for applying a current to the heaters 14, are formed on the heaters 14. A passivation layer 18 is formed on the insulating layer 12, covering the heaters 14 and the electrodes 16. Anti-cavitation layers 19 are formed on the passivation layer 18 to protect the heaters 14 from a cavitation force generated by the collapse of the bubbles.
In the inkjet printhead having the above structure, the chamber layer 20 may be formed using a method in which photosensitive epoxy is coated on the substrate 10 and the coated photosensitive epoxy is patterned, and then a top surface of the chamber layer 20 may be planarized using chemical mechanical polishing (CMP). The nozzle layer 30 may be formed using a method in which photosensitive epoxy is coated on the chamber layer 20, and then the coated photosensitive epoxy is patterned. However, it is difficult to accurately form the chamber layer 20 to a desired thickness by using conventional CMP. Since the ejection characteristic of ink droplets that are to be ejected due to ink left positioned near the nozzles 32, which is left after ink has been ejected, can be poor, it is required to manufacture a nozzle layer having an improved structure so as to improve the ejection characteristic of ink droplets.
Meanwhile, when photosensitive epoxy, which is a material constituting the chamber layer 20 and the nozzle layer 30, is patterned using a conventional photography process, it is impossible to manufacture a structure including step differences having different heights or a structure including a through hole together with a step difference.